Compressed air-operated drive-in apparatus to drive-in fastening means such as nails, staples or the like

ABSTRACT

This device is an air operated driver for nails, staples and the like. It has an actuable member and an adjustable member. When the adjustable member is in one adjusted position, actuation of the actuable member causes repeated reciprocations of a working piston in a cylinder. With the adjustable member in another position, actuation of the actuable member causes biasing one cycle of operation. In other positions of the adjustable member, various delays in cycling result. The control means comprises a main valve body and a sleeve fixed to the apparatus housing, a servo valve carrying a main control valve, an auxiliary valve, and a release valve, all guided by the main valve body and sleeve, all having an axial alignment. The servo valve is a differential piston. The auxiliary valve is located between two biasing chambers effective in opposite senses to reciprocate the auxiliary valve between two positions.

I United States Patent m1 3,583,496

[72] Inventor llellmuth Fehrs 3,278,104 10/1966 Becht et al. 227/130 Hamburg, Germany 3,323,602 6/1967 Lysell 227/130X [21] App]. No. 850,734 3,407,709 10/1968 Bade 227/130X [22] Filed Aug. 18, 1969 3,427,928. 2/1969 Bade 9 l/308X [45] Patented June 8,1971 P E [73] Assignee Joh. Freidrich Behrens Anmary xargmer j.ames Leppmk Ahernsburg, Holstein, Germany nomey 'l' Felshm {32] Priority Feb. 19, 1969 [3?] g l ogl l soti ABSTRACT: This device is an air operated driver for nails, l staples and the like. It has an actuable member and an adjustable member. When the adjustable member is in one adjusted [54] COMPRESSED AIR OPERATED DRWEJN position, actuation of the actuable member causes repeated APPARATUS To DRIVEJN FASTENING MEANS reciprocations of a working piston in a cylinder. With the ad- SUCH AS NMLS, STAPLES OR THE LIKE justable member in another position, actuation of the actuable 3' Claims 3 Drawing Figs member causes biasing one cycle of operation. In other positions of the adjustable member, various delays in cycling [52] U.S. Cl 173/15, result 91/308, 227/130 The control means comprises a main valve body and a [5 sleeve fixed to the apparatus housing a ervo valve carrying a FlEld 0 Search main control alve an auxiliary valve and a release valve a 227N471 130; 91/308 309 guided by the main valve body and sleeve, all having an axial alignment. The servo valve is a differential piston. The auxilials] References cued ry valve is located between two biasing chambers effective in UNITED STATES PATENTS opposite senses to reciprocate the auxiliary valve between two 3,278,l03 /1966 .luilfs et al 227/l positions.

l 3 7 A X l 89 27 90 5 28 30 s 29 34 3. $2 I8 7 35 2'77 i\ 36 s5 2 2324 6 E 9 37 f 4 IO 4 3 42 70 ll 7 94 so 64 I00 COMPRESSED AIR-OPERATED DRIVE-IN APPARATUS TO DRIVE-IN FASTENING MEANS SUCH AS NAILS, STAPLES OR THE LIKE The invention relates to a compressed air-operated drive-in apparatus to drive in fastening means such as nails, staples or the like with a working piston guided for to-and-fro movement in a working cylinder and a main control valve controlling the compressed air bias and compressed air release of the working piston.

With particularly simple compressed air-operated nailing apparatuses of this type the working piston is biased on one side only during the working or drive-in stroke while the return stroke of the piston is effected by means of a spring. This return spring, of course, must be loaded during the work ing stroke which considerably reduces the impact power of the working piston during the working stroke.

This disadvantage is avoided by likewise known compressed air-operated stapling apparatuses in which both the working stroke and the return stroke of the working piston biasable from both sides, are effected by compressed air. With these known apparatuses, a manually operated release lever is effective directly on the main control valve, and it is also known in connection with this apparatus to operate the compressed airoperated stapler either with single beats or with automatically repeating beats.

For the single beats, the release lever must always be actuated anew, while for the repeating blows the release lever only needs to remain permanently in its depressed position. In known apparatuses of this type, however, the control device is rather expensive and due to its complicatedness also is susceptible to trouble.

In another design of such compressed air-operated nailing apparatuses, the return of the piston into the starting position is also effected by compressed air, however, with the compressed air required for this return now being formed by a reservoir which may be connected with the compressed air source dependent upon the position of the working piston. In this manner a very simple control of the working chamber of the working cylinder is achieved which is not burdened by the control of the compressed air for the return of the working piston into its starting position.

It is known also in connection with such compressed airoperated nailing apparatuses to operate the nailing means either with single blows or with repeating blows. With these known apparatuses the pressure which forms in the reservoir is used to bear on the main control valve and its release lever, respectively, by means of a servo piston.

With these known embodiments which permit of single beats as well as automatically repeating beats, the release lever is permanently depressed for the performance of the repeating beats in that the main control valve is automatically brought into a position in which the working chamber of the working cylinder is newly biased with compressed air and then a completely new working cycle is initiated, against the force by which the release lever is actuated. In one case, an abutment connected with the working piston is effective directly on the release lever for this purpose; in another case the influence is exerted on the release lever by means of an intermediate member which is subjected to the effect of the pressure building up in the reservoir.

This direct effect on the release lever is subjected to disadvantages. With a manual actuation of the release lever, the automatic effect takes place in the form of a power exerted against the power exerted by the operator which has been found to be disagreeable. In any case, a complicated construction of the entire control system will be the result.

The invention deals with the problem of providing a compressed air-operated nailing apparatus of the type characterized, which is capable of performing both single beats and repeating beats, and which is connected with a simple control device which above all is self-contained and easy to overlook.

control valve, which leads to a quick bias of the working piston and thus a beating stroke of high kinetic energy.

According to the invention, the problem is solved in that there is an auxiliary valve arranged between the servo valve and the release valve, said auxiliary valve comprising two biasing spaces effective in opposite senses, one of them which in the following is designated also as the release valve space, being controllable by means of the release valvein such. a manner that, with the release valve actuated, it may be con nected with the high-pressure source and with the release valve not actuated it may be connected with the atmosphere, while the other space which in the following will be designated also as main valve space is in communication with a control channel controlled by the main control valve unit formed of the main control valve and the servo valve in such a manner that with the main control valve open it is in communication with the source of compressed air and with the main control valve closed is in communication with the atmosphere.-

With the control device thus designed in accordance with the invention, therefore, also the release lever must be continuously depressed to obtain a repetitive sequence of blows. But the repeating effect now no longer takes place through a momentary return movement of the release lever back into its starting position but in dependence upon the automatically reciprocating auxiliary valve. The release lever which is constantly depressed to obtain the repeating effect, in this way, remains at rest.

Of course, also this repeating lever may be somehow remotely actuated by means of a servo power, rather than manually. This remote actuation may be performed with the aid of compressed air. But a remote electric, hydraulic or electrohydraulic actuation is likewise possible. Another advantage obtained by the invention consists in that the possibility of operating the compressed air-operated nailing apparatus also with a repetitive beat sequence is completely independent of the manner in which the working piston is returned into its starting position. It is possible to effect the return movement with the aid of a reservoir which is filled in dependence upon the position of the working piston.

This type of return movement already constitutes only a simplified embodiment of a double-acting bias on the working piston. But it is also possible in some other way to bias the working piston on both sides thereby moving it into its starting position. Finally, the return movement of the working piston into its starting position is possible also with the aid of a spring.

The control device designed in accordance with the invention provides for the possibility of a repetitive sequence of beats independently of the manner in which the piston is returned into its starting position.

This advantageous effect of the invention results from the fact that to perform the repetitive sequence of beats use is made directly of the compressed air source by, on the one hand, the main control valve unit and, on the other hand, the release valve serving to control the two biasing chambers of the auxiliary control valve.

Preferably, a delay chamber is interposed in the conduit connecting the control channel with the main valve chamber. With the aid of this delay chamber, a greater volume is provided between the main control channel and the main valve chamber of the auxiliary control valve. In case of automatic return of the main control valve unit into its starting position this delay chamber must first be completely filled with compressed air before the pressure stemming from the compressed air may reach a sufficiently high value to move the auxiliary control valve into a position in which the main control valve unit starts closing the main control valve. It is obtained in this manner that the working piston has sufficient time to perform a beating stroke. It is only at about the end of the said beating stroke that, with the repetitive sequence of beats, the main valve control unit will start moving into the closed position under the influence of the compressed air bias of the main valve chamber of the auxiliary control valve.

In connection it is also recommendable to make the remaining conduits for the connection of the control channel with the main valve chamber relatively narrow so that here an additional throttling will result.

Another suitable embodiment of the subject matter of the invention is characterized in that an adjustable shutoff device is interposed in the conduit connecting the control channel with the main valve chamber which is adapted to throttle and shutoff the passage. With the aid such a throttling it is possible when carrying out the repetitive sequence of beats to delay the beginning and reduce the speed of the automatic return movement of the main control valve unit into its closing position, and of the subsequent movement into the opening position, in any extent that may be desired. If, however, the shutoff device which is interposed in this connecting conduit is closed, the possibility of the repetitive sequence of beats is precluded. The apparatus then works in the usual manner with the possibility of performing only single beats in that the release lever must be returned and actuated anew either manually or with the aid ofa servo power for each new beat.

In addition, it is recommendable to connect the control opening with the atmosphere via a channel via which also the working chamber of the working cylinder may be connected with the atmosphere. In this manner, it is additionally secured that when performing the repetitive sequence of beats the main valve chamber of the main control valve the relieved to approximately atmospheric pressure only when the working piston has approximately finished his return movement into the starting position. This effect is a result of the feature that during the return movement of the working piston into its starting position all the channels which connect the working chamber of the working piston with the atmosphere are filled with the air expelled from the working piston, i.e. are under a certain overpressure. In now in accordance with the invention the control channel of the main control valve unit is in communication with these exhaust channels, the main valve chamber of the auxiliary control valve may be completely relieved from pressure when the pressure in the exhaust channels has dropped to about atmospheric pressure. But this will be the case only after the working piston has approximately terminated his return movement, i.e. when there is no air exiting any longer to atmosphere.

In a preferred embodiment of the invention the servo valve is designed in a manner known per se as a differential piston the smaller area of which is constantly subjected to the source of the compressed air. The greater area of the said differential piston is subjected to the influence of the pressure source when the release valve is not actuated whereby the differential piston presses the main control valve into the closing position. When actuating the release valve the larger area of the differential piston is connected with the atmosphere, i.e. relieved from pressure, so that the pressure of the pressure source effective on the smaller area of the differential piston quickly moves the main control valve into the open position.

But the invention may also be carried out in connection with other embodiments of the servo valve, for instance, also in an embodiment in which the servo valve is moved by compressed air only in the one direction and by spring force in the other. With the main valve control unit formed of the main control valve and the servo valve it is neither necessary to fasten the main control valve directly on the piston of the servo valve. The servo valve and the main control valve need to be operatively connected with each other only in that, for example, the main control valve is moved in the one direction by the piston of the servo valve and in the other direction is moved by spring force.

The invention will now be explained in more detail by way of the enclosed drawing showing by way of example one embodiment of the invention in a simplified representation. Further suitable developments of the invention will be represented in connection with the following specification.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. ll shows a sectional view of the working piston and control valve arrangement of a compressed air-operated stapling apparatus according to the invention, the parts being shown in the starting position with the release valve not actuated,

FIG. 2 shows a sectional view similar to that of FIG. 1 but with the valve arrangement shown in the open condition and the working piston disposed in its lower dead center position,

FIG. 3 is a sectional view similar to that one of FIG. l but wherein after the performance ofa drive-in beat to carry out a repetitive sequence of beats the release valve has remained open by depression of the release lever and, as a result of the open position of this release valve, the main control valve including its servo valve have automatically returned to their closing position.

DESCRIPTION OF THE PREFERRED EMBODIMENT The drive-in apparatus essentially consists of a housing l with a working cylinder 2 having a working piston 5 arranged therein for to-and-fro displacement under the influence of compressed air. The housing l is designed in the form of a handle 3 having a compressed air supply chamber provided therein which is in communication with a compressed air source via a hose or the like.

The working piston drives, in a manner known per se, a drive-in stem 6 which serves to drive-in staples, nails or the like into a workpiece (not shown). The staples or nails are arranged in a magazine 79 and are supplied to a stem supply channel 30 which consists of the two components fill and 32. The magazine 79 may, besides, be of any suitable construction and therefore will not be explained in any more detail.

The cylinder 2 is closed towards the outside by means of a screw cap 8 with the interposition of a buffer 83 and an, in particular, transversely polarized permanent magnet 7 of high coercive field strength. When the upper surface of the working piston S is biased with compressed air, the permanent magnet will retain it until such time that the compressed air has built up essentially in its full height over the entire area of the working piston.

The handle 3 of the housing serves to accommodate a control valve arrangement which in general is designated by numeral d and is pushed into a reception bore 9 of the housing ll from below. This reception bore 9 is provided with a thread 10 at the outer end which serves to threadably receive a correspondingly designed threaded end of the valve main body llll of the control valve arrangement 4, the length of which is almost coextensive with the entire control valve arrangement, and to accommodate the guide for all the control members.

The valve main body 11 is inserted in the housing bore 9 in such a manner that a shoulder 12 provided thereon is pressed against the end face 13 of a guiding sleeve 14. The opposite end and closure face 77 of this guiding sleeve 14 is supported by a shoulder 7b of the housing bore 9. In this arrangement, the guiding sleeve M is sealed with respect to the housing by means ofa sealing 15.

The housing bore 9 is communicated to the outside atmosphere on the one hand via conduit or line 17 extending through the compressed air chamber 30. The conduit 17 terminates in an annular groove 84 which surrounds the housing bore 9 and has a slightly greater diameter than the latter.

On the other hand, the housing bore 9 is connected with the upper part of the working cylinder 2 via a channel 29 in that the sleeve 2 is provided with corresponding passage openings or windows. This upper side of the working cylinder will be designated in the following also as a working chamber. The channel 29 serves to supply the compressed air to this working chamber and to discharge the pressurized exhaust air to the atmosphere.

Passages 16 formed radially in the guiding sleeve 14 connect the discharge channel 17 and the annular groove 84, respectively, with a chamber 19 which is provided below the upper shoulder 85 of the guiding sleeve 14. This chamber 19 is in turn in communication with a chamber 18 via an annular channel 20, which chamber is connected with the channel 29 leading to the working chamber of the cylinder. The annular channel 20 is formed between the bore of the upper shoulder 85, the guiding sleeve 14 and a servo or pilot control valve having fastened thereon the valve member 28 of the main control valve, formed of plastic material.

In the guiding sleeve there are provided in addition a radial bore 21 and an axial bore 22 which connect the annular channel 20 with the annular space 23 which is provided between the shoulder 12 of the valve main body 11 and the end face 13 of the guiding sleeve 14.

In the chamber defined by the guiding sleeve 14 and a neck 24 of the valve body 11, there is supported for axial displacement the servo valve 25 of the main control valve 28 which has already been mentioned above. This servo valve 25 is designed as a differential piston, the biasing area 26 of which is essentially greater than the opposite end face or biasing area 27. The main control valve 28 assumes two limit positions which are determined in that the main control valve member 28 which concentrically surrounds the periphery of the shaft of the servo valve 25, contacts abutments formed on the one hand by the housing 1 and on the other hand by the guiding sleeve 14. ln the closed position, (F168. 1 and 3) the valve member contacts a stop 86 formed by the housing of the compressed air-operated nailing apparatus, and in the open position (HO. 2) it contacts the end face 77 of the guiding sleeve 14.

In the lower limit position of the main control valve body 28 (see FIG. 2) in which it rests against the end face 77 of the guiding sleeve 14, the channel 29 leading to the working chamber of the cylinder 2 is connected with the pressure chamber 30 via the now uncovered opening 87 and thereby is connected with the source of compressed air. The connection between the room 18 and the discharge line 17 is blocked in that the lower area of the main control valve 28 sealingly lies against the shoulder area 77 of the guiding sleeve 14. The servo or pilot control valve 25 is sealingly guided on the neck 24 of the valve main body 11 with the aid of a bore provided therein. An annular space 36 is arranged inside two sealings 31, 32 which are provided in spaced arrangement on the outer surface of the neck 24, said annular space being in communication with a radially extending control channel 34 provided in the servo valve 25.

The bore 88 of the servo valve 25 in which the servo valve is displaceably guided and supported on the neck 24 of the valve main body is provided with a step 89 towards the upper end from which on the bore 88 passes over into an enlarged bore 90.

ln the lower limit position of the valve main body 28 and the pertaining servo valve 25 shown in FIG. 2, the upper sealing 31 is disposed above the annular step 89 so that a free annular space 91 is formed between this sealing 31 and the outer periphery of the neck 24. In the lower limit position of the main valve body 28 and thus of the servo valve 25, accordingly, the annular space 36 is freely communicating with the compressed air chamber 30 and thus with the source of compressed air. The source of compressed air is in communication with the annular space 23 via the annular space 36, the control channel 34, the radial bore 21 and the axial bore 22, which is provided between the end face 12 of the valve main body 11 and the end face 13 of the guiding sleeve 14. In this lower limit position of the main valve body 28, the annular space 20 is additionally closed with respect to the atmosphere by means of an O-ring 35 provided on the servo valve 25 (F IG. 2).

In the upper limit position of the main valve body 28 (please see especially FIG. 1, but also FIG. 2) the upper working chamber of the cylinder 2 is communicated with the discharge line 17 via the channel 29, while the connection with the compressed air chamber 30 and thus with the source of compressed air is blocked. The communication between the channel 29 and the discharge line 17 takes place via the chamber 18, the annular space 20, the space 19 below the shoulder 85, the radial passage channels 16 in the guiding sleeve 14 and the annular groove 84. In addition, with the main valve body 28 and the pertaining servo valve 25 in the upper limit position, the annular space 36 and thus also the control channel 34 are blocked from the compressed air source in that the upper O- ring 31 is located within the guide 88 of the servo valve. The radial bore 21 however, is now connected to the discharge line via the annular channel 20, the space 19 below the upper shoulder of the guiding sleeve 14, the windows or radial bores 16 thereof, and the annular groove 84, that means is connected with the atmosphere. The annular space 37 below the large area of the servo valve 25 is now in communication with the compressed air chamber 30 via radial bores 48, radial enlargement 93, and an axial bore 39 of the main valve member, and thus with the source of compressed air in that this space is closed against the atmosphere by means of an O- ring 38 provided on the large piston of the servo valve 25.

In this manner, it is now possible for the compressed air for operation to move the servo valve 25 and with it the main valve body 28 into the closed position shown in FIGS. 1 and 3.

The valve main body 11 is provided with a center bore of different diameters extending the entire length thereof. The upper bore 39 already mentioned is in constant communication with the compressed air for operation. The lower bores 40 and 41 are stepwisely increased in size and serve to receive an auxiliary control valve 42 which has both diameters thereof axially displaceably supported in the said bores 40, 41 of the valve main body 11. This auxiliary control valve 42 which is provided in accordance with the invention possesses an axially extending piston shaft 43 of reduced diameter the outer periphery of which is provided with sealings 44, 45 and 46 in the form of O-rings. The piston shaft 43 is provided with a restricted annular portion 92 between the O-rings 45 and 46. The piston portion 94 of the auxiliary control valve 42 is greater in diameter than the piston shank 43 and is displaceably guided in the bore 41 of the valve main body 11. The annular space which is arranged above this greater piston 94 and surrounds the piston shank 43 of the auxiliary control valve 42, is referenced 47 and in the following will be designated also as main valve chamber. The space below said piston 94 of greater diameter is referenced 55 and will be designated also as release valve chamber in the following. The sealing 46 blocks this main valve space 47 with respect to the atmosphere which is in communication with the restriction 92 of the piston shaft 43 of the auxiliary control valve 42 via a bore 49 provided in the valve main body 11.

The sealing rings 44, 45 formed as O-rings and likewise provided on the piston shaft 43 of the auxiliary control valve 42 control the aeration and venting of the biasing chamber 37 below the large diameter of the servo valve 25.

The radial bores of the valve main body 11 already mentioned above which are in communication with the biasing chamber 37 do not directly terminate in its bores 40 but via an enlarged annular space 93. In the upper limit position of the main valve body 28, the sealing ring 44 is in the region of the radial enlargement 93 of the bore 40 and thus connects the bore 39 which is in communication with the compressed air for operation, with the annular biasing space 37 via the bore 40 and the radial bores 48. In this arrangement, the sealing ring 45 seals the connection between this chamber 37 and the bore 49 which is in communication with the atmosphere.

In the lower limit position of the main valve body 28 which is shown in F 16. 2, the sealing ring 45 is disposed adjacent the radial enlargement 93 of the bore 40 of the valve main body 11. The biasing chamber 37 of the servo valve 25 accordingly is now in communication with the atmosphere via the radial bores 48, the radial enlargement 93, the annular space between the piston shaft 43 and the bore 40 of the main valve member 11, the annular restriction 92 and the bore 49. The sealing 44 seals the radial enlargement 93 with respect to the bore which is in communication with the compressed air for operation. The spaces between the sealing rings 44 and 45 are selected to be such that there occurs no intersection of aerating and venting of the space 37 whereby essentially quicker shifting speeds of the servo valve 25 and thus the main valve 28 are obtained.

In the region of its end facing towards the trigger lever 50 the central bore 41 of the main valve body is closed by a screwed plug 51 which is likewise provided with a center bore 52 of different diameters having supported therein for axial displacement a release pin 53 designed as a valve body. The screwed plug 51 limits the movement of the auxiliary control valve 42 towards the outside (downwards), in that the auxiliary control valve 42 when in the lower position lies closely against an end face provided at the screwed plug 51. The biasing space 55 forming below the large piston 94 is designated as release valve chamber as already mentioned above. This release valve chamber 55 is aerated and vented, i.e. controlled, by means of the release valve 53 which is designed as a pin. When aerated, this release valve chamber 55 is communicated with the source of compressed air in a manner to be described in more detail in the following. The compressed air then becomes effective via the end face 56, on the auxiliary control valve 42. This end face is larger than the upper end face 57 of the piston shaft 43 of the auxiliary control valve 42. The 39 bore in the screwed pin comprises a smaller bore 60, a larger bore 52 and astill slightly larger bore 98. That end of the bore 60 which faces towards the inlet opening 87 has a valve seat 97 provided thereon, while between the two bores 52 and 98 there is arranged a valve seat 96. The valve seat 96 cooperated with an O-ring 62 arranged on the release valve pin 53 which here is effective as a valve housing. In a corresponding manner, the valve seat 97 cooperates with an O- ring 99effective as a valve housing. In order to bias the release valve space 55 with compressed air, the release valve pin 53 is moved upwardly as shown in FIGS. 2 and 3 by means of the release valve lever 50. In this position, the release valve chamber 55 is in communication with the bore 99 via bores 58 provided in the screwed pin 51, a space 59, a channel 64 extending axially along the bore 60, and thus is in communication with the compressed air for operation. In this position, the O-ring 62 lies close against the valve seat 96 and thus closes the communication with the atmosphere. At the same time, the O-ring 99 has moved away from the valve seat surface 97 and has opened this communication.

But if the release pin 53 is in the lower position as shown in FIG. I, the release valve chamber 55 will be in communication with the atmosphere in that the sealing ring 62 has moved away from the valve seat 96. The communication with the source of compressed air is simultaneously interrupted in that the O-ring 99 has seated itselfon the valve seat 97.

A partial region of the valve main body 11 is covered by a threaded sleeve 65 concentrically surrounding it. This threaded sleeve 65 is threadedly connected with a fine thread 66 on the outside of the valve housing and is axially adjustable through a small region. In the upper position, the bore 67 is shutoff from the sealing 68; in this position, the apparatus is set for single beat operation, and a repetitive sequence of beats is not possible. In the lower position the bore 67 is exposed. The apparatus may now be operated with a repetitive sequence of beats with only the release lever 50 having to be permanently depressed. In the intermediate position of the threaded sleeve, the automatically controlled movement of the servo valve 25, and thus of the main valve housing 28 may be influenced. In the following, the details of the individual Figures will be described more precisely.

As already explained above, FIG. 1 shows the drive-in apparatus in the position of rest. The working piston is disposed in its upper end position. The main valve housing 28 blocks the communication between the working cylinder and the compressed air conduit 30 for operation in that the elastic main valve body 28 has the upper end face thereof lying close against the seating surface 86 of the housing I.

The working chamber of the working cylinder 2 is in communication with the atmosphere via the channel 29, the chamber 18, the annular channel 20, the chamber 19, the passage channels 16, the annular groove 84 and the outlet channel 17. The bore 39 of the servo valve 25 as well as the bore 61 of the auxiliary control valve 42 are constantly connected with the conduit 30 for compressed air for operation so that the end face 57 of the auxiliary control valve 42 is biased with compressed air and is axially displaced into the lower limit position. The sealing ring 44 of the auxiliary valve 42 is disposed in the radial enlargement 93 of the bore 40 of the main valve body 11 and thus is out of engagement so that the biasing space 37 is in communication with the compressed air for operation via the bore 48, the annular enlargement 93-, the bore 61 and the bore 39. The sealing 45 is engaged and blocks the communication of the biasing chamber 37 with the atmosphere (via the conduit 49). In the biasing chamber 37, the large area 26 of the servo valve is biased which is effective in a sense opposite to the smaller end face 27 thereof. In this manner the main valve body 28 is pressed against the valve surface 86 of the housing 3 by its upper surface 72.

The compressed air for operation present in the bore 61 of the auxiliary control valve is effective against the end face 75 of the release valve pin 53 and presses the sealing 99 against the upper seat 97 of the screwed pin 51.

The sealing 62 has moved away from the valve seating surface 96 of the screwed pin 51 by a certain distance so that the release valve chamber 55 is in communication with the atmosphere via the bore 58, the chamber 59 and the annular space 63 which forms between the bore 98 of the threaded pin 51 and the release valve pin 53.

When adjusted for single shot" the threaded sleeve 65 is in its upper position in which the sealing ring 68 covers the bore When adjusted for automatic," the bore 67 is exposed whereby the main valve chamber 47 in the position as shown in FIG. I is in communication with the atmosphere in a manner now to be described in more detail. The chamber 23 mentioned above is for this purpose in communication with an axial bore 69 which merges with the bore 67 which is in turn in communication with the bores 100 via the bore 67 controlled by the sealing ring 68, said bores 100 passing over into delaying chamber 70 of increased volume. This delaying chamber 70 of increased volume is in communication with the main valve chamber 47 via a bore 71.

If the valve or sealing ring 68 has been moved into the open position, i.e. into the Automatic position by means of the threaded sleeve 65, then, in the position as shown in FIG. 1, the main valve chamber 47 will be in communication with the atmosphere, namely via the bore 71, the delay chamber 70, the bore 100, the radial bore 67, the axial bore 69, the annular chamber 23, the axial bore 22, the radial bore 21, the annular space 20, the space 19, and the conduit 17.

In accordance with FIG. 2, the release valve pin 53 has been lifted by means of the release lever 50 againstits downwardly directed axial force, and the sealing 62 has been pressed against the sealing or valve surface 96 of the threaded plug 51. Thereby, the communication of the release valve chamber 55 with the atmosphere has been blocked. The communication of this chamber with the compressed air conduit for operation, however, has been opened, namely via the passage 64, the opened valve sealing 99, the bore 61 of the auxiliary control valve 42 and the bore 39 of the servo valve.

The end face 56 of the auxiliary control valve 42 is biased with compressed air from the release valve chamber 55. As soon as the pressure building up in this chamber has reached a value such that the force effective on the area 56 is greater than the force effective on the upper surface 57, the auxiliary control valve will experience an axial displacement upwardly.

This displacement is continued until the upper end face 57 of the auxiliary valve lies close against the corresponding end face of the valve main body 11. in this position, the sealing 44 of the auxiliary valve 42 blocks the communication of the biasing chamber 37 with the bore 39 and thus with the compressed air line 30 for operation, in that simultaneously the sealing 45 which now is in the region of the radial enlargement 93, releases this biasing chamber 37 via the radial enlargement 93, the radial restriction 92 and the conduit 49, to the atmosphere. The pressure drop of the working pressure present in the biasing chamber 37 down to the atmospheric pressure here takes place suddenly. That means that the force which due to the bias of the lower end face 26 of the servo valve 25 is axially directed upwardly, drops quickly down to zero in that simultaneously the force constantly directed axially downwardly against the upper end face of the servo valve 25, moves the servo valve 25 downwards at high speed and opens the main valve at the same high speed.

The servo valve 25 moves the main valve member 28 away from the seating surface 86 of the housing 1 and moves it towards the seat or end face 77 of the guiding sleeve 14 until finally the main valve body 28 is pressed by its under surface against the valve or end face 77 of the guiding sleeve 14 by the servo valve 25. Thereby the chamber 18 which is in communication with the working chamber of the working cylinder 2 via the passage 29 is shutoff from the atmosphere (see FIG. 2). At the same time, the working chamber of the working cylinder 2 is communicated with the compressed air chamber 30 via the channel 29 and the opening 87, said compressed air chamber 30 being in communication with the source of compressed air. The compressed air accordingly biases the working piston from the upper surface. After substantially full working pressure has been built up over the area of the working piston 5, the power generated in this way will be in a position to overcome the retaining power of the permanent magnet 7. The working piston now performs its working stroke with a high degree of acceleration.

ln order to move the working piston 5 back again into its final or starting position, the main control valve 28 must be closed again, and thus must lie against the seating surface 86 of the housing by its upper area. As already explained above, when adjusting the apparatus to single shot the threaded sleeve is threaded upwardly in the drawings so that the ring or valve seal 68 will close the axial bore 67. in this manner, the main valve chamber 47 is not communicated with either the source of compressed air or the atmosphere. lf, when set for single-shot operation, the release lever 50 releases the release valve pin 53, the latter will be returned to its starting position as shown in FlG. 1. This is effected by the influence of the compressed air on the surface 75 of the release valve pin 53 exposed thereto, in that simultaneously the sealing ring 62 leaves its seat 96 and releases the annular channel 63 leading to the atmosphere. In that hereby the sealing or valve ring 99 of the release valve pin 53 lies sealingly against the valve seat 97, the communication of the release valve chamber 55 with the compressed air chamber 30 is interrupted. At the same time, the communication of this release valve chamber with the atmosphere is established via the now exposed annular channel. The compressed air present in the release valve chamber 55 may now escape to the atmosphere, the result of which is that the force due to the compressed air from the chamber 30 being effective against the upwardly facing end face 57 of the auxiliary control valve 42, will push this auxiliary control valve 42 downwardly into the position as shown in FIG. 1. The upper sealing ring 44 of the auxiliary control valve now lies inside the annular recess 93 of the bore 40 of the guiding sleeve 11, so that the compressed air chamber 30 is connected with the biasing chamber 37 via the bore 39. the annular recess 93 and the bore 48. The compressed air now exerts a pressure on the larger under surface of the servo valve 25 designed as a differential piston, so that the servo valve is again moved into its upper position shown in FIG. 1, in which the upper surface of the main control valve 28 lies close to the valve seating surface 86 and blocks the communication between the compressed air chamber 30 and the working chamber.

As has been explained above, the sealing or valve ring 68 is removed out of the region of the bore 67 by means of the threaded sleeve 65 so that when the release lever 50 is permanently depressed, the main valve chamber 47 is automatically communicated with the source of compressed air or the atmosphere in a manner to be described in the following, such that a continuous or repetitive sequence of beats will result.

When set to Automatic thus, the release valve pin 53 will constantly remain in its upper position shown in FlGS. 2 and 3 so that the release valve chamber 55 is biased with compressed air for operation from the compressed air chamber 30 and this compressed air exerts a pressure against the surface 56 of the auxiliary control valve 42 in such a manner that it will be disposed in its upper position as shown in FIG. 2.

The reversal of the main control valve 42 from this position into its position shown in FIG. 1, therefore, must take place automatically via a pressure pulse which contrary to the force exerted on the area 56 by the compressed air for operation and effective in an upward direction in the Figures, will exert an axially downwardly directed force ofdisplacement. For this purpose, the main valve space 47 is filled with compressed air for operation which becomes effective on the annular surface 74 from this space 47. The communication of this main valve chamber 47 on the one hand with the source of compressed air and, on the other. hand, with the atmosphere is controlled by means of the main control valve 28 and the servo valve 25 connected thereto, respectively. In this connection it does not matter either functionally or constructionally whether the control is effected directly by means of the main control valve 28 or by means of the servo valve 25, because it is the purpose of the servo valve 25 to move the main control valve functionally in the correct manner. The servo valve and the main control valve 28 thus are moving essentially uniformly and in timed relationship, i.c. even in case they should not be combined into a unit as is the case with the example of embodiment.

Only after the main control valve 28 has been fully opened by means of the servo valve 25, Le. has reached its lower limit position as shown in FIG. 2, will the main valve chamber 47 be communicated with the compressed air chamber 30 and thus with the source of compressed air, namely via the second bore of the servo valve, the annular chamber 36 between the sealings 31 and 32 of the valve main body 11, the essentially radially extending control channel 34 in the servo valve 25, the radial bore 21, and the axial bore 22 in the guide sleeve 14, the annular space 23 between the end face 13 of the guiding sleeve 14 and the end face 12 of the valve main body 11, the axial bore 69 and the radial bore 67 in the valve main body 11, the annular space between the threaded sleeve 65 and the valve main body 11, the delaying chamber 70 and the bore 71 (please see FIG. 3).

The compressed air for operation introduced into this main valve chamber 47 builds up with delay and exerts an axially downwardly directed displacement forces as shown in FIG. 3, on the area 74 of the auxiliary control valve 42 only after the delaying chamber 70 has been completely filled with compressed air for operation and essentially the full pressure of the compressed air for operation prevails in the main valve chamber 47.

It is also the purpose to provide the conduits leading from the delaying chamber 70 to the main valve chamber 47 with a relatively narrow cross-sectional area so that here as well a certain throttling effect will occur when the pressure builds up in the main valve chamber 47.

The time ofdelay is fixed to be such that the working piston 5 wili have safely performed its full working stroke and its full return stroke and there will yet be sufficient time afterwards to fill the air return chamber 76. Only after these working steps have been completed will the auxiliary control valve 42 ac- 7 icordingly move from the position shown in HO. 2 to the posi- E ii tion shown in FlG. 3. In this manner, the auxiliary control valve in turn connects the working chamber 37 with the source of compressed air for operation (see FIG. 3). The compressed air is effective on the large piston area 26 of the servo valve 25 designed in the form of a differential piston, from the working chamber 37, and consequently urges the servo valve 25 into its upper position shown in FIG. 3, in which the main control valve 28 blocks the working chamber of the working cylinder 2 from the compressed air chamber 39 and in this working chamber is simultaneously communicated with the atmosphere via the line 17, asjust described. The compressed air present in the main valve chamber 437, with a position as shown in FIG. 3, may escape only with delay because the compressed air escaping from the main valve chamber 437 impinges on the air which is pushed into the atmosphere with a certain overpressure through the channel 29 and the conduit 17 during the return stroke of the working piston 5. The compressed air present in the main valve chamber 47, of course, may escape only via the bore 71, the delaying chamber 70 and the annular space E00, the bores 67 and 69 of the main valve body 11, the annular chamber 23, the bores 22 and 21l of the guiding sleeve M, the annular channel 20 and the chamber 19 below the shoulder 85 of the guiding sleeve lll. But here the air escaping from the main valve space 47 impinges on the air draining from the working chamber of the working cylinder but which is now expelled with increased energy and with the higher pressure because the working piston just is biased from below with the compressed air of the air return chamber 76.

The drain of the air from the main valve chamber 47 and thus the relief of this chamber from pressure are delayed until the working piston 5 no longer expels any air, i.e. until the working piston 5 has reached its upper end position. it is not before now that the pressure in the main valve chamber 47 may decrease to atmospheric pressure and, as a result, the auxiliary control valve is returned into the position as shown in FIG. 2 under the influence of the compressed air constantly efiective on its area 56 from the release valve chamber 57, the next beat taking place in this position.

it is thus secured in this manner, that with the threaded sleeve 65 adjusted for automatic operation, the auxiliary control valve 42 will be automatically switched not until the working piston 5 has reached its end positions. The speed of the working cycle may be varied by adjustment of the annular valve seal 68 in that the passage between the bore 67 and the annular space we is more or less throttled. But also with such a throttle position of the annular seal 63 the auxiliary control valve 42 is essentially shifted only in the end positions of the working piston 5 because the effect of the delaying chamber and the delaying effect due on the one hand to the delaying chamber 70 and, on the other hand, to the fact that the main valve chamber 47 is communicated with the annular channel 20 for the purpose of pressure relief at a moment at which also the working chamber of the working cylinder 2 is pressure-relieved via this annular channel, i.e. is communicated with the atmosphere, are not influenced by described throttle position. The pressure relief of the main valve chamber 47, under these circumstances will take place in the above-described manner essentially only after the working chamber of the working cylinder 2 has been relieved from pressure.

lclaim:

1. Compressed air-operated drive-in apparatus to drive in fasteners such as nails, staples or the like, said apparatus comprising a housing, a working cylinder in the housing, a working piston guided in the cylinder for reciprocation relative thereto, and means to cause relative reciprocation between said piston and cylinder, said means comprising means to supply a compressed air bias to said housing, means to relieve said compressed air bias from the housing, a main control valve controlling the passage of said compressed air bias to said cylinder and allowing passage of compressed air bias to the working cylinder when said main control valve is open and shutting off communication between the compressed air bias and said cylinder and establishing communication between said cylinder and said compressed air relief means when said main control valve is closed, a servo control valve having means to move said main control valve, and being coaxial therewith, means to bias said servo valve with compressed air bias, a release valve, an auxiliary control valve disposed between said release valve and servo valve, means providing two biasing chambers on opposite sides of said auxiliary control valve, and effective in opposed senses with respect to said auxiliary control valve, means to actuate said release valve, means to cause one of said chambers to communicate with said compressed air bias when the release valve is actuated, and to communicate with the atmosphere when the release valve is not actuated, means to provide a control opening, conduit means connecting said control opening with said other chamber, and means controlled by said main control valve and said servo valve to cause said control opening to be in communication with said compressed air bias, with the main control valve open, and to be in communication with the atmosphere, with the main control valve closed.

2. The combination of claim 1, and a delaying chamber interposed in said conduit means.

3. The combination of claim ll, and adjustable means to throttle and block said conduit means.

43. The combination of claim 2, and adjustable means to throttle and block said conduit means.

5. The combination of claim 1, the communication of said control opening with the atmosphere, with said main control valve open, being via a channel which connects the working cylinder with the atmosphere, with the main control valve closed.

6. The combination of claim 5, and a delaying chamber interposed in said conduit means.

7. The combination of claim 6, and adjustable means to throttle and block said conduit means.

8. The combination of claim 5, and adjustable means to throttle and block said conduit means.

9. The combination of claim ll, said servo valve comprising a differential piston, means being provided to subject said piston to greater compressed air bias pressure in a direction to close said main control valve, than in an opposite direction, upon subjecting said servo valve to compressed air bias at both ends and closing said main control valve, and to subject said servo valve to compressed air bias only in said opposite direction at one end and opening the opposite end of said servo valve to the atmosphere, to thereby move said main control valve to open position, and said main control valve being fastened on said servo valve.

110. The combination of claim 9, and a delaying chamber interposed in said conduit means.

llll. The combination of claim 9, and adjustable means to throttle and block said conduit means.

Ill. The combination of claim 10, and adjustable means to throttle and block said conduit means.

113. The combination of claim 1, said auxiliary control valve and said release valve being coaxial with said servo valve and main control valve.

114. The combination of claim 1, a main valve body, and a guiding sleeve coaxial with said body, fixed in said housing and serving as carriers for said servo valve and said auxiliary control valve.

1.5. The combination of claim 14, said servo valve, main control valve and auxiliary control valve being coaxial with said main valve body and guiding sleeve.

16. The combination of claim 1, and means dependent upon the adjustable means being in one position for causing said main control valve to open and close, repeatedly, upon actuating said release valve and keeping said release valve in actuated condition, and dependent upon said adjustable member being in another position, to open and close said main control valve once, upon actuating said release valve and keeping it actuated.

17. The combination of claim 16, and dependent upon said adjustable member being in still another position to throttle said conduit means.

18. The combination of claim 17, said adjustable means having means for blocking said conduit means, in its position for causing said main control to open and close once upon actuating said release valve and keeping it actuated.

19. Compressed air-operated drive-in apparatus to drive in fasteners such as nails, staples or the like, said apparatus comprising a housing, a working cylinder in said housing, a working piston guided in said cylinder for reciprocation relative thereto, and means to cause relative reciprocation between said piston and cylinder, said means comprising means to supply a compressed air bias to said housing, means to relieve said compressed air bias from said housing, a main control valve controlling passage of compressed air bias to said cylinder and allowing passage of compressed air bias to said working cylinder when said main control valve is open and shutting off communication between the compressed air bias and said cylinder and establishing communication between said cylinder and said compressed air relief means, when said main control valve is closed, means to mount said member for movement relative to said housing, a single actuable member, an adjustable member, means to mount said adjustable member for movement relative to said housing, and means to cause said main control valve to open and close repeatedly upon actuating said actuable member and keeping it actuated, with said adjustable member in one adjusted position thereof, and to cause said main control valve to open and close once only upon actuating said actuable member and keeping it actuated, with said adjustable member in another adjusted position thereof.

20. The combination of claim 19, and to vary the rate of opening and closing of said main control valve with said adjustable member in other adjusted positions thereof.

21. The combination of claim 14, and means on said guiding sleeve to limit movement of said main control valve in one direction.

22. The combination of claim 21, and means on said main valve body to limit movement of said auxiliary control valve in opposite directions.

23. The combination of claim 14, and means on said main valve body to limit movement of said release valve in opposite directions.

24. The combination of claim 21, and means on said housing to limit movement of said main control valve in an opposite direction.

25. An air-operated tool for driving in fasteners, said tool comprising a housing, a cylinder in said housing, a piston in said cylinder, said housing having a chamber for compressed air, said chamber having an opening communicating with said cylinder, a compressed air relief in the housing communicating with said cylinder, a tubular valve body fixed in said housing, a tubular servo control valve slidably mounted on the outside of said valve body, means on said servo control valve to close said opening, in one position thereof, and to open said opening in another position thereof, said valve body having an axial through hole in constant communication with said opening and chamber, a tubular auxiliary valve control slidably mounted inside said tubular valve body and having an axial hole communicating with said axial hole in said valve body, a release valve axially mounted in the lower end of said valve body and projecting into said axial hole of said auxiliary control valve, means to actuate said release valve, and means controlled by actuation of said release valve, to reciprocate said auxiliary control valve, and means controlled by said auxiliary control valve, to reciprocate said servo control valve, to open and close said opening, and to shut off and open communication between said compressed air relief and said cylinder.

26. The combination of claim 25, means adjustably mounted on said valve body means, and means dependent on the adjusted position of said adjustable member, to limit the reciprocation of said auxiliary control valve and servo valve to one cycle each upon actuating said release valve and keeping it closed, or to automatic repeating cycling upon actuating the release valve and keeping it actuated.

27. The combination of claim 26, and means also dependent on the position of said adjustable member to vary the rate of cycling.

28. The combination of claim 25, said auxiliary control valve forming, with said valve'body, a release valve chamber at one end thereof, and a main valve chamber at its opposed end, and means to open said release valve chamber to the atmosphere, and to also open said main valve chamber to compressed air relief, when said release valve is unactuated, and to open one side of said servo valve to greater compressed air pressure than to the other side thereof, to maintain said servo control valve in position to close said opening.

29. The combination of claim 28, means to cause said release valve chamber to open to said compressed air chamber, and said main valve chamber to open to compressed air from said compressed air chamber, upon actuating said release valve and keeping it actuated, and also to cut off compressed air from said one side of said servo control valve, while continuing to subject the other side of said servo valve to compressed air, to move said servo control valve to open position, to allow compressed air to pass to said cylinder and to shut communication between said cylinder and compressed air relief.

30. The combination of claim 29, adjustable means, and means dependent on the position of said adjustable means, to automatically repeatedly cycle said servo control valve or to cycle said servo control valve once only, upon actuating said release valve and keeping it actuated.

31. The combination of claim 30, said means dependent on the position of said adjustable means, comprising a channel formed in the valve body and leading to the atmosphere, and means in one position of the auxiliary control member, to connect said one side of said servo control valve to said channel and to close said side of said servo control valve to compressed air, and in another position of said auxiliary control valve; to close said side of said servo control valve from said channel, and to open said side of said servo control valve to compressed air from said chamber, and said adjustable member in one position thereof uncovering said channel and in another position thereof covering and closing said channel. 

1. Compressed air-operated drive-in apparatus to drive in fasteners such as nails, staples or the like, said apparatus comprising a housing, a working cylinder in the housing, a working piston guided in the cylinder for reciprocation relative thereto, and means to cause relative reciprocation between said piston and cylinder, said means comprising means to supply a compressed air bias to said housing, means to relieve said compressed air bias from the housing, a main control valve controlling the passage of said compressed air bias to said cylinder and allowing passage of compressed air bias to the working cylinder when said main control valve is open and shutting off communication between the compressed air bias and said cylinder and establishing communication between said cylinder and said compressed air relief means when said main control valve is closed, a servo control valve having means to move said main control valve, and being coaxial therewith, means to bias said servo valve with compressed air bias, a release valve, an auxiliary control valve disposed between said release valve and servo valve, means providing two biasing chambers on opposite sides of said auxiliary control valve, and effective in opposed senses with respect to said auxiliary control valve, means to actuate said release valve, means to cause one of said chambers to communicate with said compressed air bias when the release valve is actuated, and to communicate with the atmosphere when the release valve is not actuated, means to provide a control opening, conduit means connecting said control opening with said other chamber, and means controlled by said main control valve and said servo valve to cause said control opening to be in communication with said compressed air bias, with the main control valve open, and to be in communication with the atmosphere, with the main control valve closed.
 2. The combination of claim 1, and a delaying chamber interposed in said conduit means.
 3. The combination of claim 1, and adjustable means to throttle and block said conduit means.
 4. The combination of claim 2, and adjustable means to throttle and block said conduit means.
 5. The combination of claim 1, the communication of said control opening with the atmosphere, with said main control valve open, being via a channel which connects the working cylinder with the atmosphere, with the main control valve closed.
 6. The combination of claim 5, and a delaying chamber interposed in said conduit means.
 7. The combination of claim 6, and adjustable means to throttle and block said conduit means.
 8. The combination of claim 5, and adjustable means to throttle and block said conduit means.
 9. The combination of claim 1, said servo valve comprising a differential piston, means being provided to subject said piston to greater compressed air bias pressure in a direction to close said main control valve, than in an opposite direction, upon subjecting said servo valve to compressed air bias at both ends and closing said main control valve, and to subject said servo valve to compressed air bias only in said opposite direction at one end and opening the opposite end of said servo valve to the atmosphere, to thereby move said main control valve to open position, and said main control valve being fastened on said servo valve.
 10. The combination of claim 9, and a delaying chamber interposed in said conduit means.
 11. The combination of claim 9, and adjustable means to throttle and block said conduit means.
 12. The combination of claim 10, and adjustable means to throttle and block said conduit means.
 13. The combination of claim 1, said auxiliary control valve and said release valve being coaxial with said servo valve and main control valve.
 14. The combination of claim 1, a main valve body, and a guiding sleeve coaxial with said body, fixed in said housing and serving as carriers for said servo valve and said auxiliary control valve.
 15. The combination of claim 14, said servo valve, main control valve and auxiliary control valve being coaxial with said main valve body and guiding sleeve.
 16. The combination of claim 1, and means dependent upon the adjustable means being in one position for causing said main control valve to open and close, repeatedly, upon actuating said release valve and keeping said release valve in actuated condition, and dependent upon said adjustable member being in another position, to open and close said main control valve once, upon actuatiNg said release valve and keeping it actuated.
 17. The combination of claim 16, and dependent upon said adjustable member being in still another position to throttle said conduit means.
 18. The combination of claim 17, said adjustable means having means for blocking said conduit means, in its position for causing said main control to open and close once upon actuating said release valve and keeping it actuated.
 19. Compressed air-operated drive-in apparatus to drive in fasteners such as nails, staples or the like, said apparatus comprising a housing, a working cylinder in said housing, a working piston guided in said cylinder for reciprocation relative thereto, and means to cause relative reciprocation between said piston and cylinder, said means comprising means to supply a compressed air bias to said housing, means to relieve said compressed air bias from said housing, a main control valve controlling passage of compressed air bias to said cylinder and allowing passage of compressed air bias to said working cylinder when said main control valve is open and shutting off communication between the compressed air bias and said cylinder and establishing communication between said cylinder and said compressed air relief means, when said main control valve is closed, means to mount said member for movement relative to said housing, a single actuable member, an adjustable member, means to mount said adjustable member for movement relative to said housing, and means to cause said main control valve to open and close repeatedly upon actuating said actuable member and keeping it actuated, with said adjustable member in one adjusted position thereof, and to cause said main control valve to open and close once only upon actuating said actuable member and keeping it actuated, with said adjustable member in another adjusted position thereof.
 20. The combination of claim 19, and to vary the rate of opening and closing of said main control valve with said adjustable member in other adjusted positions thereof.
 21. The combination of claim 14, and means on said guiding sleeve to limit movement of said main control valve in one direction.
 22. The combination of claim 21, and means on said main valve body to limit movement of said auxiliary control valve in opposite directions.
 23. The combination of claim 14, and means on said main valve body to limit movement of said release valve in opposite directions.
 24. The combination of claim 21, and means on said housing to limit movement of said main control valve in an opposite direction.
 25. An air-operated tool for driving in fasteners, said tool comprising a housing, a cylinder in said housing, a piston in said cylinder, said housing having a chamber for compressed air, said chamber having an opening communicating with said cylinder, a compressed air relief in the housing communicating with said cylinder, a tubular valve body fixed in said housing, a tubular servo control valve slidably mounted on the outside of said valve body, means on said servo control valve to close said opening, in one position thereof, and to open said opening in another position thereof, said valve body having an axial through hole in constant communication with said opening and chamber, a tubular auxiliary valve control slidably mounted inside said tubular valve body and having an axial hole communicating with said axial hole in said valve body, a release valve axially mounted in the lower end of said valve body and projecting into said axial hole of said auxiliary control valve, means to actuate said release valve, and means controlled by actuation of said release valve, to reciprocate said auxiliary control valve, and means controlled by said auxiliary control valve, to reciprocate said servo control valve, to open and close said opening, and to shut off and open communication between said compressed air relief and said cylinder.
 26. The combination of claim 25, means adjustably mounted on said valve body means, and means dependent on the adjusted position of said adjustable member, to limit the reciprocation of said auxiliary control valve and servo valve to one cycle each upon actuating said release valve and keeping it closed, or to automatic repeating cycling upon actuating the release valve and keeping it actuated.
 27. The combination of claim 26, and means also dependent on the position of said adjustable member to vary the rate of cycling.
 28. The combination of claim 25, said auxiliary control valve forming, with said valve body, a release valve chamber at one end thereof, and a main valve chamber at its opposed end, and means to open said release valve chamber to the atmosphere, and to also open said main valve chamber to compressed air relief, when said release valve is unactuated, and to open one side of said servo valve to greater compressed air pressure than to the other side thereof, to maintain said servo control valve in position to close said opening.
 29. The combination of claim 28, means to cause said release valve chamber to open to said compressed air chamber, and said main valve chamber to open to compressed air from said compressed air chamber, upon actuating said release valve and keeping it actuated, and also to cut off compressed air from said one side of said servo control valve, while continuing to subject the other side of said servo valve to compressed air, to move said servo control valve to open position, to allow compressed air to pass to said cylinder and to shut communication between said cylinder and compressed air relief.
 30. The combination of claim 29, adjustable means, and means dependent on the position of said adjustable means, to automatically repeatedly cycle said servo control valve or to cycle said servo control valve once only, upon actuating said release valve and keeping it actuated.
 31. The combination of claim 30, said means dependent on the position of said adjustable means, comprising a channel formed in the valve body and leading to the atmosphere, and means in one position of the auxiliary control member, to connect said one side of said servo control valve to said channel and to close said side of said servo control valve to compressed air, and in another position of said auxiliary control valve; to close said side of said servo control valve from said channel, and to open said side of said servo control valve to compressed air from said chamber, and said adjustable member in one position thereof uncovering said channel and in another position thereof covering and closing said channel. 